<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
		<script type="text/javascript">
			//交换两个变量的值(数据)
			var num1 = 1;
			var num2 = 2;
			var temp;
			//将num1里面的值,赋值一份拷贝给temp
			temp = num1;//1
			num1 = num2;//2
			num2 = temp;//1
			
			
			alert(num1)//2;
			alert(num2)//1;
			var a;
			var b;
			
			
			
			
			num1 = 10;
			alert(num1);
		</script>
	</body>
</html>
